suspend-on-idle: Allow disabling suspending for specific devices
Sometimes it would be nice to disable module-suspend-on-idle for
specific devices. For me the use case is to keep a HDMI sink running
all the time to avoid loss of audio when starting to play a stream to
the device (the HDMI receiver eats a bit from the beginning of the
stream when the device is opened). This is arguably a hacky solution
to the problem, but on the other hand, I think it's very sensible to
interpret negative timeout in the module-suspend-on-idle.timeout
property as disabling the suspending altogher. This is also how the
exit-idle-time configuration option behaves (negative value disables
automatic exiting).
I moved the property parsing from the timer restart function to the
function that creates the device_info objects, because if the timeout
is negative, we don't need to create the device_info object at all.